The present invention relates to a key switch to be mounted on a controller for a game machine or the like.
A related-art key switch of this type will be described with reference to FIG. 3. In the drawing, a key switch 1 has, in a guide hole 3 which is formed in a case 2 of a controller for a game machine or the like, a key top 4, a click rubber 5 which is formed in a lower part of the key top 4 integrally with the key top 4, a movable contact 6 formed of an electrically conductive body which is provided on a lower face of a head 5a of the click rubber, and fixed contacts 8 which are provided on a circuit board 7 positioned below the movable contact 6.
The click rubber 5 is formed in the shape of a bowl, and the moveable contact 6 is provided on an inner face of the head 5a of the click rubber 5 as described above in such a manner that the movable contact 6 can be contacted with and detached from the fixed contacts 8 by elastic force of the click rubber 5 that is adapted to be flexed and restored according to motions for striking the key top 4.
Moreover, a circumferential edge of the click rubber 5 at its lower end is bent upwardly to form a recess 9 at a bent part. In the recess 9, a guide wall 10 for defining the guide hole 3 holds the click rubber 5 at its lower end, thereby to fix the click rubber 5 inside the case 2.
In the related-art, there is interposed a slight gap M between the guide wall for defining the guide hole that is formed in the case and the key top that is idly inserted inside the guide wall so as to move vertically.
Accordingly, fatty oils of a user""s hand my adhere to the top when the key top is struck, and the fatty oils that have adhered to the key top often fall along a peripheral face of the key top through the gap M to adhere to the click rubber. On such occasions, there will occur in may cases such inconveniences that since the click rubber will be swollen with the fatty oils, the feeling of a click may be lost and a smooth function of key stroke cannot be performed.
It is therefore an object of the present invention to provide a key switch for preventing fatty oils of a user""s hand which have adhered to a key top from directly adhering to a click rubber, so that the function of the click rubber may be fully performed.
In order to achieve the above object, according to the present invention, there is provided a key switch, comprising:
a key top, including a body part having a first width and a flange formed on a lower end portion of the body part so as to have a second width which is larger than the first width;
a click rubber, provided on a bottom face of the body part of the key top, the click rubber being elastically deformable such that the key top is vertically moved between an upper first position and a lower second position;
a case, formed with a first chamber having a third width which is larger than the first width but smaller than the second width, for accommodating the body part of the key top therein, and a second chamber continued from the first chamber and having a fourth width which is larger than the second width, for accommodating the flange of the key top and the click rubber therein.
Consequently, the fatty oils of a user""s hand that have adhered to the key top will be received by the flange even though the fatty oils fall down at the stroke of the key top, and the fatty oils will not reach the click rubber in the lower part. Therefore, such drawbacks in the prior art that the click rubber may be swollen with the fatty oils that have adhered to the click rubber resulting in a loss of the feeling of a click and a smooth switching motion cannot be performed. Hence, a malfunction occurring in the key stroke operation will be eliminated. Further, since not only the fatty oils but other foreign substances will not get in direct contact with the click rubber, quality of the key switch will also be improved.
Preferably, an upper face of the flange is abutted against a ceiling part of the second chamber when the key top is placed in the upper first position.
The above described preventive effect for fatty oils or foreign substances can be further enhanced.
Preferably, a recess is formed in a ceiling part of the second chamber. A protrusion is formed on an upper face of the flange. The protrusion is fitted into the recess when the key top is placed in the upper first position.
Since the fatty oils and the foreign substances are accommodated within a recess defined by an outer periphery of the body part and the protrusion, the above described preventive effect for fatty oils or foreign substances can be further enhanced.